Meteorites as Food Source on Early Earth: Growth, Selection, and Inhibition of a Microbial Community on a Carbonaceous Chondrite.

Meteoritic material accumulated on the surface of the anoxic early Earth during the Late Heavy Bombardment around 4.0 Gya and may have provided Earth's surface with extraterrestrial nutrients and energy sources. This research investigates the growth of an anaerobic microbial community from pond sediment on native and pyrolyzed (heat-treated) carbonaceous chondrite Cold Bokkeveld. The community was grown anaerobically in liquid media. Native Cold Bokkeveld supported the growth of a phylogenetically clustered subset of the original pond community by habitat filtering. The anaerobic community on meteorite was dominated by the Deltaproteobacteria Geobacteraceae and Desulfuromonadaceae. Members of these taxa are known to use elemental sulfur and ferric iron as electron acceptors, and organic compounds as electron donors. Pyrolyzed Cold Bokkeveld, however, was inhibitory to the growth of the microbial community. These results show that carbonaceous chondrites can support and select for a specific anaerobic microbial community, but that pyrolysis, for example by geothermal activity, could inhibit microbial growth and toxify the material. This research shows that extraterrestrial meteoritic material can shape the abundance and composition of anaerobic microbial ecosystems with implications for early Earth. These results also provide a basis to design anaerobic material processing of asteroidal material for future human settlement.